Bimetallic salts and derivatives thereof their preparation and use in the complexing of ligands

ABSTRACT

BIMETALIC SALTS, HAVING THE GENERIC FORMULA MM&#39;&#39;XN WHEREIN M IS A GROUP I-B METAL, M&#39;&#39; IS A GROUP III-A METAL, X IS A HALIDE AND N IS EQUAL TO THE SUM OF THE VALENCES OF M AND M&#39;&#39;, ARE PREPARED BY REACTING THE HALOGEN SALTS OF THE INDIVIDUAL METALS, M AND M&#39;&#39;, IN A SUITABLE SOLVENT. THE BIMETALLIC SALT FORMED THEREBY IS A DISCRETE MONOMERIC SPECIES AND CAN BE UTILIZED IN THE SEPARATION AND RECOVERY OF VARIOUS LIGANDS, BY PREFERENTIAL COMPLEXATION. COMPLEXATION CAN BE CONDUCTED WITH THE BIMETALLIC   SALT IN THE SOLID STATE, IN SOLUTION, OR AS A SLURRY, AND WITH THE COMPLEXIBLE LIGAND IN THE GASES OR LIQUID STATE. THE LIGAND IS RECOVERED BY DECOMPLEXATION OF THE BIMETALLIC SALT-LIGAND COMPLEX OR BY DISPLACEMENT OF THE COMPLEXED LIGAND WITH ANOTHER LIGAND.

March 1972 R. B. LONG ETAL 3,651,159

BIMETALLIC SALTS AND DERIVATIVES THEREOF, THEIR PREPARATION AND USE IN THE COMPLEXING OF LIGANDS Filed Sept. 5, 1968 Figure I EFFECT OF TEMPERATURE ON ETHYLENE, PROPYLENE AND CO EQUILIBRIA WITH (TOLUENE) Cu A|CI PROPYLENE ETHYLE/VE E O '2' 0 IO u E .2 3 5' O LLI LO E Temperofure,C I l 1 '00 so 25 o l I I l 25 3.0 3.5 440 IOOO/T K R8 [M9 Qfl Began By Attorney 3,&l,l59 BllMnTALLlIC SALTS AND DERIVATIVES THERE- OF, THEIR PREPARATION AND USE IN THE COMPLEXTNG OF LTGANDS Robert B. Long, Atlantic Highlands, and Fred A. Caruso, Elizabeth, N..l., Richard J. de Fee, Baton Rouge, La., and David G. Walker, Baytown, Tex.; said Long, said Caruso, and said do Feo assignors to Esso Research and Engineering Company Filed Sept. 3, M68, Ser. No. 895,912 (Filed under Rule 47(b) and 35 U.S.C. 118) a 7 int. 63!. C07c 7/00, J1/00;li01j 11/22 US. Cl. 2606o7 31 Claim ABSTRACT OF THE DliSQLOSURE Bimetallic salts, having the generic formula MMX wherein M is a Group I-B metal, M is a Group III-A metal, X is a halide and n is equal to the sum of the valences of M and M, are prepared by reacting the halogen salts of the individual metals, M and M, in a suitable solvent. The bimetallic salt formed thereby is a discrete monomeric species and can be utilized in the separation and recovery of various ligands, by preferential complexation. Complexation can be conducted with the bimetallic salt in the solid state, in solution, or as a slurry, and with the complexible ligand in the gases or liquid state. The ligand is recovered by decomplexation of the bimetallic salt-ligand complex or by displacement of the complexed ligand with another ligand.

FIELD OF THE INVENTION This invention relates to the preparation and use of novel monomeric bimetallic salts having the generic formula MMX wherein M is a Group I-B metal, M is a Group III-A metal, X is a halide, and n is equal to the sum of the valences of M and M. More particularly, this invention relates to the use of these novel salts in the separation and recovery, by preferential complexation, of various ligands, i.e., electron donors. In another embodiment hereof, this invention relates to the preparation and use of novel complexes of these bimetallic salts having the generic formula MMX L wherein M, M, X, and n are as described, L is a ligand, e.g., a hydrocarbon, and m is equal to the complexing stoichiometry of L and is an integer from 14.

PRIOR ART The use of various salts as sorbents (complexing agents) for the separation and recovery, i.e., purification, of various ligands is well known to the art. Such salts as cuprous ammonium acetate and cuprous halides, e.g., cuprous chloride, have been widely employed to recover ligands such as acetylenes, butadiene, carbon monoxide, monoolefins, etc. While the use of such salts has generally been successful, several disadvantages are associated with their use. Thus, the salts, particularly the cuprous ammonium acetate, do not have wide applicability and have been useful in recovering only a few different ligands. The cuprous halides, although possessing the ability to recover several types of ligands, necessitate the use of rather severe conditions. To illustrate, cuprous chloride has been found useful for complexing ethylene, e.g., as from ethane/ ethylene streams. However, because the ethylene-cuprous chloride complex is relatively unstable, i.e., has a high dissociation pressure, at room temperatures and atmospheric conditions, it is necessary to employ low temperatures and/or high pressures to make ethylene recovery feasible. Thus, at atmospheric pressure, ethylene complexing starts at 16 F. and at 0 F. only a 44 Wt. percent recovery from 50 wt. percent ethylene streams can be obtained. Now, since commercial operations re- 3,651,159 Patented Mar. 21, 1972 quire better than a 90 wt. percent recovery, temperatures must be in the range of -35 F. to F. with several hundred p.s.i. pressure to achieve such results. Obviously, compression and/ or refrigeration costs greatly increase the cost of producing ethylene in this manner.

It has now been found, however, that ethylene recovery, for example, in excess of wt. percent, preferably in excess of wt. percent, more preferably in excess of 99 wt. percent, e.g., 99.9 wt. percent, can be achieved at room temperature and ambient pressures and that the purity of ethylene so recovered will be inexcess of 99 wt. percent, when the invention to be described herein is utilized. Moreover, this invention provides a sorbent that is more versatile than those previously in use, i.e., it is applicable to a wide variety of ligands, has a greater capacity for sorbing ligands, and generally overcomes all of the shortcomings of prior art sorbents.

As used herein, the term ligand is defined as a complexible molecule, generally an unsaturated compound, capable of donating a pair of electrons and capable of forming a coordinating bond with a metal, M, as in 2(CH )-CH=CH -CuAlCl where the two propylene molecules are coordinated to the copper atom. Also, the term complex" as used herein is meant to include adsorption as well as absorption and the product formed thereby, the process generally being referred to as sorption wherein a sorbent (salt) sorbs (complexes) a sorbate (ligand) and the complex may then be desorbed (decomplexed).

SUMMARY OF THE INVENTION In accordance with this invention, therefore, monomeric bimetallic salts having the formula MMX wherein M is a Group I-B metal, M is a Group III-A metal, X is a halide, and n is equal to the sum of the valences of M and M, are prepared by reacting the respective halides of M and M, the halide of M preferably being present in an excess, in the presence of a suitable reaction medium, generally a solvent for the Group III-A metal halide. The monomeric bimetallic salt can then be easily recovered, e. g., by driving off the solvent and/or filtering away excess Group I-B salt, and utilized in the sorption of various ligands, such as acetylene, monoolefins, poly olefins, conjugated diolefins, aromatics, cyclic olefins, carbon monoxide, etc., and generally those compounds designated as ligands.

The bimetallic salts prepared in accordance herewith are discrete monomeric species and are to be distinguished from the crystalline, polymeric materials reported by Amma, JACS, 85, 4046 (1963), and Turner and Amma, JACS, 88, 1877 (1966). These references report the formation of crystalline structures made up of infinite zigzagging sheets composed of tetrahedral Cu(l) and AlCLf, the structure being reported in the former article as:

C H Cl Cl Cl 6,6 C H 9 o 0 a a a o o 0 CU Al 0 o 0 I Cu 0 0 Cl C H C1 C1 Cl a a I Cu Al l a C6H6 Cl C1 C1 C1 C H6 o o o q o 0 I 0 i o o 0 Cu Al Cu a n 0 I c1 C6H6 o a o e o a Thus, the Cu(I)+ ion is bonded to Cl atoms of three different AlCl4- tetrahedra and a benzene ring making the Cu(I)+ ion four coordinate. The latter article further supports this structure and presents X-ray data to prove that the complex forms pleated crystalline sheets with adjacent sheets being held together by van der Waals forces.

From an examination of the structure reported in the literature, it is readily apparent that the benzene to Cu(I) mole ratio is 1:1 throughout the polymeric structure and the generic formula for such a polymer can be written as (C H -CuAlCl wherein n represents a number much greater than one. It is believed that the crystalline polymer reported resulted from the manner in which it was prepared, i.e., in an evacuated system using dry benzene and anhydrous resublimed cuprous chloride and anhydrous resublimed aluminum chloride. Nevertheless, the procedure utilized herein, i.e., reacting halides of M and M in a suitable solvent such as an aromatic, gives rise to a structure believed to be a discrete monomeric species which can be pictured as having the structural formula:

Cu Al and its benzene derivative 1) 0511a /C1 /C1 CoHs C1 \C1 From Formula II it is apparent that the benzene to Cu(I) mole ratio is 2:1 and that the generic formula can be written as (C H -CuAlCl which is structurally far different from that reported by Amma. Moreover, an examination of the two structures reveals that the Cu(I) of Amma is bonded to three separate Al through C1 bridges, whereas the structure of Formula II shows the Cu(I) bonded to but one Al through only two Cl bridges. Clearly, then, a different structure having rather different properties is reported herein, e.g., in the complexing of aromatics such as benzene a 100% increase in stoichiometry over the Amma structure can be obtained.

The difference in preparative technique which is believed to account for the difference in structure and properties reported herein is believed to be due to the codissolving, with reaction, of the respective metal halides in a stoichiometric amount of, for example, an aromatic such as benzene, such that two moles of aromatic are present for each mole of bimetallic salt (see Formula II). A clear solution is obtained which contains no free, i.e., unbonded, aromatic, and which chemically analyzes for (aromatic) -MM'X This structure is evidenced by data obtained from chemical analysis of stoichiometry and nuclear magnetic resonance (NMR) studies. Thus, after exchanging the aromatic complex with propylene, NMR studies of a (propylene) 'CuAlCl sample showed that the Al was tetrahedrally bound to four Cl atoms and that two propylene molecules were complexed.

The invention described herein has several distinct advantages over prior art complexing agents such as CuCl in that (1) a Wide variety of ligands can be complexed at ambient conditions, due to the stabilizing influence of the Group III-A metal salt; (2) ligand to copper mole ratios in excess of 1:1 can be achieved, whereas CuCl could carry only one mole of monoolefin or one-half mole of diolefin per mole of copper; and (3) aromatics can be 4 complexed whereas prior art compounds were capable of complexing only aliphatic hydrocarbons.

The monomeric bimetallic salts have been described herein as having the generic formula MM'X Thus, M is a Group I-B metal, i.e., copper, silver, or gold, copper (I) being particularly preferred. M is a Group III-A metal, i.e., boron, aluminum, gallium, indium, thallium, while boron and aluminum are preferred, aluminum being particularly preferred. X is a halide, i.e., fluoride, chloride, bromide, iodide, and chlorine and bromine are preferred, particularly chlorine. The most preferred bimetallic salts are CuAlCl, and CuAlBr particularly the chloride derivative, while other representative salts are CuBF CuBCl AgBF AgBCl AgA1Cl AgAlBr CuGaCl CuInCl CuThCl and the like.

The monomeric bimetallic salts of this invention are readily prepared by reacting the respective halides of M and M in a suitable reaction medium. Since the bimetallic salt will generally be soluble, to some extent, in the same solvents as the Group III-A metal salt, it is preferred to employ as a reaction medium, a solvent in which one of the salts of either M or M is soluble or partially soluble and the other is insoluble or relatively insoluble. Thus, Group III-A metal halides, such as AlCl are generally soluble in aromatics, e.g., (J -C aromatics, preferably c o more preferably C -C aromatics such as benzene, toluene, Xylene, mesitylene, and most preferably toluene. On the other hand, Group I-B metal halides, such as CuCl, are soluble in C C monoolefins, preferably C -C more preferably C -C monoolefins, e.g., ethylene, propylene, isobutylene, butenes, hexenes, heptenes, and the like, most preferably alpha monoolefins. Aromatic solvents, however, are most advantageously utilized.

Of course, other components may also be present during the reaction so long as a solvent in which one salt is relatively soluble and the other is relatively insoluble is present, and two such solvents may be present, e.g., reacting a solution of CuCl in a monoolefin and a solution of AlCl in an aromatic. Now, since the bimetallic salt will complex with a variety of compounds, including such compounds, i.e., ligands, as aromatics and monoolefins, a complex having the greatest stability will form, and, in this instance, the monoolefin complex being more stable than an aromatic complex will form.

Other illustrative preparative techniques that may be employed involve contacting solid CuCl with an aromatic solution of AlCl thereby forming a solution of CuAlCl, (aromatic) 2 complex in the aromatic; contacting CuCl slurried in a parafiin, e.g., a C -C paraffin, with an aromatic solution of AlCl contacting solid AlCl or AlCl slurry with a solution of CuCl in a monoolefin, thereby forming a precipitate or solution of CuAlCl -(monoolefin) and any other combination that may be desirable under the circumstances. Preferably, the solvent is employed in a stoichiometric relationship to the bimetallic salt product. Thus, for aromatics and monoolefins, such as ethylene or propylene, the stoichiometric relationship can be one or two, preferably two, and, therefore, two moles of solvent are then employed for each mole of cuprous chloride and aluminum chloride utilized.

The complex may then be recovered, e.g., by filtering, decanting, etc. the precipitated CuAlCl -(olefin) complex, or driving oif excess solvent from CuAlCL, (aromatic) 2 and soluble CuAlCl (olefin) complexes and the bimetal- Iic salt obtained by decomplexing the complex, e.g., by heat and/or reduced pressure. A typical preparation technique is illustrated herein as (Ar aromatic, S:solid, Sl:slurry, L=liquid):

Filter EC HLt Decent Heat Vacuum t f u t z mzhm 112% ine which the respective M and M halides can be contacted i can range from about 40 to 300 F. These temperatures are practical limits since below about -40 F. most of the preferred aromatic solvents, or their complexes, tend to solidify while above about 300 F. the

most preferred C -C aromatics tend to boil, unless prep aration is carried out above atmospheric pressure. Preferably, temperatures range from about 0 to 150 F. Pressures, too, may vary and subatmospheric as well as superatmohpheric pressures can be employed, for example,

0.1 to 1000 psi, preferably atmospheric to 100 psi.

However, conditions of room temperature, i.e., 18-25 C. and atmospheric pressure can be advantageously employed.

One factor of considerable importance in the preparation of these novel salts relates to the catalytic activity of free Group IIIA metal salts such as the highly active Friedel-Crafts catalyst AlCl In order to eliminate free AlCl for example, an excess of the Group l-B salt is preferably employed, thereby insuring that all the AlCl reacts. It is only necessary that some excess Group I-B salt is present; however, preferably, the molar ratio of Group IB metal salt/Group III-A metal salt is at least 1.01, and more preferably ranges from about 1.02 to 1.2. Additional Group I-B metal salt could be employed but this would generally lead to excess solids in the reaction medium, when an aromatic solvent is employed, and these would only have to be removed, e.g., by filtration. This procedure generally inhibits or neutralizes catalytic activity of the sorbent for all but the most reactive of compounds, e.g., higher monoolefins or diolefins.

The starting materials utilized for the reaction should be of substantial purity, e.g., 99+% pure. Thus, recrystallized CuCl can be employed and AlCl can be purified by heating while fluidizing with nitrogen and blowing out any HCl or H O that may be present. Further, the halides should be stored in the absence of oxygen and water which tend to oxidize and hydrolyze the components, respectively. Similarly, the reaction to form the bimetallic salt and any reactions (sorbing processes) in which the bimetallic salt is employed should preferably be run under substantially anhydrous conditions and in the substantial absence of oxygen. Generally, however, Water and oxygen can be present in amounts similar to that tolerated by Ziegler type catalysts, e.g., less than about 10 ppm. water or oxygen. Additionally, the solvent selected for preparing the bimetallic salt should not be capable of being polymerized by the Group TIL-A metal halide and only inert reaction media should be employed. Thus, aromatic solvents are far more preferred than monoolefinic solvents.

and separation and recovery, in highly concentrated forms, of various ligands. The salts are quite versatile and may be employed as solutions (in aromatics) or as liquid complexes of CuAlCl -(aromatic) as a solid (fluidized or fixed bed), or as slurries (in parafiins with or Without aromatic activators) and can be contacted with ligands wherein the ligand can be in either the gaseous or liquid states. Thus, it is only necessary that the salt and the ligand be placed in intimate contact and this is readily achieved by normal gas-solid, gas-liquid, liquidsolid, liquid-liquid contacting means. However, it is generally preferred to take advantage of the physical state of the ligand in fixing the contacting means. Thus, if the ligand is gaseous, the sorbent is generally liquid, and, if the ligand is liquid, the sorbent may be liquid or solid. It is noted generally that when the sorbent is employed as a solid, the ligand recovery is increased as the temperature of the ligand approaches its dew point, that is, a ligand should be within 30 F. of its dew point, preferably within 20 F., more preferably within 10 F. of its dew point, with these temperatures above the dew point when utilizing a solid bimetallic sorbent.

A wide variety of ligands can be complexed, i.e., sorbed, by these novel bimetallic salts. Among these are unsaturated compounds such as olefins, acetylenes, aromatics, carbon monoxide, and the like. More specifically, the unsaturated hydrocarbons can be (a) acetylenes, such as C C acetylenes, preferably C -C acetylenes, e.g., acetylene, methyl acetylene, ethyl acetylene, dimethyl acetylene, vinyl acetylene, etc.; (b) monoolefins, such as C -C monoolefins, preferably C -C more preferably C -C monoolefins, most particularly ethylene and propylene; (c) conjugated diolefins, such as C -C conjugated diolefins, preferably C -C conjugated diolefins, e.g., butadiene, isoprene, etc.; ((1) polyolefins, such as c o preferably C C polyolefins, e.g., cyclododecatriene, cyclooctadiene; (e) cyclic olefins and alicyclic olefins, such as C C preferably C C e.g., cyclopentene, cyclohexene, cyclooctene, etc; (f) aromatics, such as C C aromatics, preferably C C aromatics, e.g., benzene, xylene, toluene; and (g) cumulative di olefins, such as C -C cumulative diolefins, e.g., allene. The process is particularly applicable to sorbing C CJ, monoolefins, C CA, acetylenes, carbon monoxide, and C C aromatics. Any of the foregoing ligands can be sorbed by the salt itself, while derivatives thereof, e.g., CuAlCl -(aromatic) will sorb any ligand having a greater complex stability, i.e., an exchange reaction will occur, the more stable ligand displacing the less stable ligand.

Generally, the compound to be sorbed, i.e., separated by preferential complexation, and recovered is contained in a feed stream admixed with various other compounds which are either not sorbed or less preferentially sorbed, i.e., their complexes are less stable than the complex of the compound to be preferentially sorbed. For example, such feed streams as ethane/ethylene or propane/propylene (the paraflin not being sorbed) can be treated to concentrate the olefin. In cases, however, Where several ligands can be horbed, e.g., when a solid sorbent or slurry is employed, the complexed ligands can be decomplexed as a whole, or individually, and recovered by distillation or fractional decomplexing, respectively.

While the stability of various complexes will vary Widely, it can generally be stated that monoolefin complexes are more stable than acetylene complexes which, in turn, are more stable than carbon monoxide complexes which, in turn, are more stable than aromatic complexes. In monoolefin complexes, propylene complexes are more stable than ethylene complexes, and stability is belived to be related to molecular weight. Because of the wide range of ligands available for complexing, it is understood that several compounds of each class mentioned herein will overlap compounds of other classes. Nevertheless, one skilled in the art can readily determine, by routine experimentation, the exact order of stability for any set of complexes.

The bimetallic salt can be used as a dry solid, in a slurry with diluents such as C -C paraffins, C -C naphthenes, or as a solution in (I -C aromatics of C C cycloolefins. Of course, when aromatic solutions are employed, the aromatic complex is believed to form (and the sorbent is then the aromatic complex rather than the salt alone), but since the aromatic complex is the least stable relative to the various other complexible ligands, the aromatic is readily displaced by the desired ligand, and the aromatic complex is a preferred sorbent because it is a liquid sorbent. Each of the sorbing techniques mentioned has advantages and disadvantages regarding its use. For example, the complexing of ethylene with CuAlCl as a dry solid or a paraffn slurry gives an invariant equilibrium constant while the use of a toluene or other aromatic solution or liquid aromatic complex of CuAlCl, gives a solution equilibrium which depends upon the amount of reactants and products present. The invariant equilibrium has the advantage of permitting all of the CuAlCL, to be consumed in the process while the solution type equilibrium limits conversion by the formation of free aromatc (by displacement) and the consumption of the (aromatic) -CuAlCl complex. On the other hand, product yield is limited by the dissociation pressure of the (ethylene) -CuAlCl complex in the invariant case whereas complete product recovery can be obtained in the solution case. It is generally preferred, however, to employ aromatic solutions, i.e., liquid aromatic complexes, (because of their ease in handling, e.g., heat of complexation is readily dissipated both because it is balanced in ligand exchange and because of easier heat transfer, intimate contact between ligand and sorbent is promoted) of the bimetallic salt or parafiin slurries activated with at least about 10 mole percent, preferably about 10 to about 300 mole percent aromatic, more preferably 100 to 150 mole percent aromatic based on the bimetallic halide salt, the aromatics being those previously described as useful for solution preparation. It is believed that activation involves solution of the bimetallic salt by the activator, e.g., C C aromatics, and increasing amounts of activator will increase the solution of salt. Thus, the use of a slurry with an aromatic activator will approach, in operation and result, the use of an aromatic solution or liquid aromatic complex as the amount of activator increases.

It is interesting to note that the number of moles of ligand per mole of copper in the bimetallic salt increases from 1:1 to 2:1, for example, in monoolefin complexes, as the system is changed from dry solid or paraflin slurry to aromatic solution or aromatic activated slurry and, therefore, the recovery of ligand is increased. This variable capacity of the salt with regard to ligands is an interesting phenomenon attendant to this invention. While the theoretical nature of this phenomenon is not yet understood, it has been determined that the complexing stoichiometry, i.e., the number of moles of ligand that will complex with one mole of bimetallic salt waries, depending upon the reaction phase, e.g., liquid sorbent, solid sorbent, and the physical state of the ligand, e.g., liquid, gas. Thus, the generic formula of the complexes formed by ligands and the bimetallic salt may be represented as MM'X L wherein M, M, X, and n have been previously described, -L is a complexible ligand as described, and m is equal to the complexing stoichiometry of the ligand and is an integer from 1 to 4. Now, since the ligands are coordinated to the M metal, e.g., Cu(I), and M has a maximum coordination number of 4, the maximum of m must be 4. The most common form of coordination of M, however, ranges from 1 to 2 (an m of 2 is shown above in Formula II). Generally, for aromatics and monolefins, m is 1 to 2, usually 2; for example, 1 when only 1 mole of aromatic is used to form the complex; for carbon monoxide and acetylene, m is usually 1, and for cumulative olefins such as allene, m is usually 1.

While in many instances herein In is shown as 2, it is believed that as the system becomes increasingly ionic, for as yet unknown reasons, one of the bonds between Cu(I) and Cl is broken, thereby allowing another ligand to complex with Cu(I), such as:

' which shows the breaking of both Cu(I) to Cl bonds.

Again, while it is apparent that m may vary from 1 to 4, depending upon the nature of the systems, little is known about the theoretical aspects of this variation. However, it is conceivable that ligand driving force may also play a role in this phenomenon and that the physical state of the ligand and sorbent may affect that driving force.

It is also noted that in the generic formula MMX L L may be the same or different. For example, an aromatic complex, such as (C H -CuAlCl can be treated with one mole of ethylene, which is a stronger complexing agent than benzene, thusly:

and treatment with another mole of ethylene yielding: (CSHS) 2 4) 4+ 2 4 2 4)2' 4+ G G the overall equation being written as: 6 6)z" 4+ 2 4) Obviously, then a variety of complexes can be formed, depending upon the relative stability of ligands and treatment ratios. Additionally, the foregoing expressions also illustrate a displacement reaction which can be utilized to recover ligands. As will be discussed hereinbelow, these displacement reactions can be made reversible so as to aid in the recovery of a variety of ligands.

One of the particular advantages of this process is that ligand recoveries can be obtained at reasonable conditions. Thus, while somewhat difierent conditions for complexing and decomplexing will apply for difierent materials, conditions are generally not critical and may vary widely. Thus, for any type of complexing, reaction temperatures may range from about 40 F. to about 300 F., preferably -40 F. to 200 F., and more preferably about 50 F. to 150 F. Pressures similarly may vary Widely and can range from about 0.5 atmosphere to about atmospheres, preferably 1 to 20 atmospheres. While decomplexing to recover a desired ligand may be carried out in a variety of ways, e.g., dissociation, displacement, decomplexing by dissociation will occur at a temperature higher than complexing (for constant pressure processes) and in the range of about 50 F. to about 500 F., preferably about 200 F. to 400 F., or at lower pressures than for complexing (for constant temperature processes) and in the range of about 0.1 to 30 atmospheres, preferably 0.5 to 20 atmospheres. Most preferably, however, liquid sorbent systems are employed, and still more preferably liquid sorbent systems with gaseous ligands are employed. In these most preferred systems, the same general conditions as already outlined will apply; however, liquid systems are only limited by those conditions under which the ligand remains liquid.

Additionally, the complexed ligand can be used as a storage device for that ligand. For example, in the case of carbon monoxide or other low boiling ligands, storage is generally effected in pressure vessels as a gas or in cryogenic containers as a liquid. In either case, rather expensive storage devices are required which are relatively hazardous, e.g., high pressures, or may result in large losses if a leak in a liquid system develops. Moreover, so long as the bimetallic salt is fully complexed, there is no danger of contamination in storage and an exceedingly high purity product can be stored and transported relatively easily Further, higher molecular weight ligands, such as aromatics, can now be stored as solids at relatively high temperatures and also can be kept for long periods in an exceedingly high state of purity.

The recovery of the complexed ligand can be effected in a variety of ways depending upon the sorbent system that is employed. For example, in a solution system, using CuAlCl (aromatic) for example, some monoolefin complexes will precipitate, e.g., the ethylene complex, and can be recovered by filtration, decantation, centrifugation, etc. Filtration, etc. can also be employed to recover such complexes from slurry systems. After separation of the complex, it can be decomplexed by heating in the presence of an inert stripping gas, e.g., nitrogen, helium, argon, carbon dioxide, and the ligand then is easily separated from the stripping gas, e.g., by condensation, distillation, etc., and the salt and slurry diluent are then recycled to the process. Obviously, the stripping gas could also be a boiling aromatic.

Another recovery method, which readily lends itself to continuous operations involves reversible displacement reactions for solution type sorbent systems, i.e., use of aromatic solvents for bimetallic salt. Such displacement reactions may be readily exemplified by the following expressions which show the recovery of propylene using a toluene complex: Complexing:

( s s s 2 4+ a s) In Equation 4 a liquid aromatic complex can be employed to recover liquid or gaseous monoolefin from a feed stream containing propane and propylene, for example. The resulting rnonoolefin complex is soluble in the liquid medium formed by liberation of liquid toluene, gaseous propane bubbling through unaffected since propane does not complex. The propylene can be recovered by heating to shift the equilibrium and stripping with inert gas or boiling toluene, Equation 5, under conditions, i.e., higher temperature and/ or lower pressure, which will favor the reverse reaction. Thus, Equations 4 and 5 may be Written as a single reversible equation. The figure attached hereto, is a log plot of equilibrium constant against temperature at constant atmospheric pressure for the reversible complexation of several ligands with a 10 (toluene) -CuAlCl complex. In this plot, by operating at lower temperatures, the products will increase, i.e., complexes of ethylene, propylene, or CO will tend to form at the expense of the toluene complex. The opposite is true for operation at higher temperatures.

As previously discussed, the use of an excess of Group I-B metal halide insures the reaction of all of the Group III-A metal halides and, therefore, substantially neutralizes the catalytic activity, e.g., alkylation, polymerization, of the Group III-A salts. Nevertheless, the bimetal lic salt may contain some residual catalytic activity due to the acid nature imparted to it by the Group III-A salt. This residual activity generally will only appear when highly reactive ligands, e.g., diolefins, such as butadiene, or C3+ monoolefins such as hexene, heptene, etc., are utilized in the sorption process. Moreover, this catalytic activity is further promoted when such reactive ligands are decomplexed by heating at high temperatures which can cause catalytic polymerization or alkylation of the desired ligand. In such cases, it is advisable to employ recovery methods such as displacement or decomplexation using pressure changes rather than using increased temperatures for decomplexation. Nevertheless, this residual catalytic activity (or acidity) can be effectively neutralized after preparation of the bimetallic salt by the use of certain additives, i.e., neutralizing agents. These neutralizing agents are generally characterized as basic materials, and are exemplified by ammonia and organic nitrogen bases which preferably have a boiling point in the same range as the reaction solvent (if a solvent is employed) so as to insure the presence of the neutralizing agent under all reaction conditions. Examples of such organic nitrogen bases are aniline, pyridine, quinoline, trimethylamine, triethylamines, tri-n-butylamine, and the like, and C -C nitrogen bases generally, Additionally Group V-B metal trihalides can be effectively employed as neutralizing agents, e.g., antimony trichloride, phosphorous trichloride, arsenic trichloride, tribromide derivatives, etc. Under normal circumstances, it is only necessary that small amounts of neutralizing agent be present, e.g., merely enough to react with free acidity of the system. In fact, the presence of too much neutralizing agent causes precipitation of copper salt from the solution leading to formation of a different catalytic species. Preferably, the neutralizing agent is present in an amount of at least about 0.01 wt. percent based on sorbent, more preferably about 0.1 wt. percent. Preferred materials are ammonia and pyridine which are preferably employed with aromatic sorbent solutions in amounts ranging from about 0.01-1 wt. percent based on sorbent. (The neutralizing agents described herein can also be employed in a like manner during the preparation of the bimetallic salt when C monoolefinic solvents are employed.)

Having now described the invention, the following examples will further serve to illustrate the preparation and use of these novel bimetallic salts. However, no limitations are to be implied from these examples since variations and modifications will be obvious to those skilled in the art.

EXAMPLE 1 1.1 moles of carefully purified CuCl (109 grams) were mixed with 1 mole of purified A101 (133 grams) in an inert nitrogen atmosphere as dry powders. This powder was slowly added with agitation in an inert atmosphere to 2 moles (156 grams) of dry benzene. The mixture was allowed to stir for one hour. The clear, dark liquid was removed from the small quantity of undissolved solids by decantation. The liquid was then treated with anhydrous ethylene gas, and a solid ethylene complex was formed. The solid was separated by filtration, and washed with pentane saturated with ethylene. The solid was dried in a stream of ethylene. The dry solid was then heated in a vacuum, and the ethylene was decomplexed yielding the 1 1 free CuAlCl Elemental analysis of the ethylene complex before decomposition showed.

Calculated (percent): Cu, 22.0; A1, 9.4; Cl, 49.1; C, 16.7; H, 2.8. Found (percent): Cu, 21.0; A1, 9.7; Cl, 53.2;

12 tion. This example shows the use of small amounts of added nitrogen base to inhibit these side reactions.

A complexing solution was prepared by dissolving 109 grams (1.1 moles) of CuCl and 133 grams (1 mole) of C, 17.1;H,3.1. 5 AlCl in 2 moles of toluene. Analysis of the resulting This analysis corresponds to CuAlCl -2(C H and clear, dark solution showed: shows a 2:1 complex, indicating that the original benzene CuAlC1t (c7H8)2 complex was a 2:1 complex.

EXAMPLE 2 Calculated (percent): C, 40.3; A1, 6.5; H, 3.9; Cl, 34.1; Cu, 15.2. Found (percent): C, 39.4; A1, 6.4; H, 4.1; CI, Various ligands were recovered using a solution sor- 34.4; Cu, 14.4. bent system of CuAlC1 in toluene prepared by dissolv- Portions of this solution were treated with a synthetic ing 232 grams of CuAlCL prepared similarly as in Ex feed containing 50% propane and 50% propylene. One ample 1 in 184 grams toluene. The ligand feed streams portion was treated as is, and a second was treated after were fed into solution as vapors by allowing the feed addition of 0.1% anhydrous ammonia. In the case of stream to bubble through the liquid and the complexed the ammonia treated sorbent, propylene was complexed ligand recovered by heating the complex to the boil- Without side reactions. In the case of the untreated soring point of the complex. Table I shows the results of bent, side reactions accounting for over 10% of the this experiment. propylene were obtained. Gas chromatographic analysis TABLE I 2 of the liquid showed the presence of alkylated aromatics and oligomers of propylene. Methyl acetylene/ Allene/ propane P p EXAMPLE 6 Feed: A CuAlBr -(benzene) com lex was re ared b a c 11111 d Mtl t1 All 4 2 P PP Y efig aimfib 2 8 procedure analogous to that for =CuAlCl -(toluene) ff f fg g hg a 0 0 This solution, clear green in color was used to separate t t i n ga 42 carbon monoxide from a feed mixture containing 21% a a gas C0 74% H and 5% CH. Com lexation was carried D 1 d a t 99.9+ 99.9 4 P ecomp exe pro no out at 800 p.s.1.g. and 25 C. The carbon monoxide was The results in thiS table clearly SheW the ability of the complexed selectively. At the end ot the feed addition, the toluene-CuAlCL, complex to remove substantially comreactor Was depressureod to 0 2- and the complex pletety the eomplexing ligand from the feed at 1.00m was decomposed at 60 C. to yield carbon monoxide of temperature and atmospheric conditions, and to produce 995% Pumy' E M the ligand upon decomplexing in exceedingly high purity. XA PLE 7 EXAMPLE 3 The use of a slurry of CuAlCl to complex ethylene from an eth lene-ethane mixture The recovery of ethylene from an ethylene/ ethane feed y at room temperature and atmospheric pressure is shown A slurry of CuAlCL; in heptane was prepared as 01- in Table II using slurry, slurry-activated, and liquid arolows: The CuAlCl -benzene complex was prepared by dismatic complex sorbents. 40 solving 109 grams (1.1 moles) of pure CuCl and 133 TABLE II (Slurry-activated) (Slurry) 34 wt. 29 wt. percent wt. percent percent CuAlCh CuAlCh in 3:1 CuAlCh in toluene Complexing agent in 110 nCv/toluene solution Ethylene content, mole percent Fee 50 50 53 Initial tail gas 1. 6 0. 7 1. 5 Deeomplexed product 99. 9+ 99. 9+ 99. 9+ Capacity: moles (Jr/cu 1 2 2 This table shows excellent recoveries of ethylene using any method; however, in the slurry-activated and solution sorbent systems, the amount of material necessary for complexation can be reduced, with corresponding reduction in process costs due to increased capacity of the sorbent for ethylene.

EXAMPLE 4 Table III shows the recovery of various ligands with a complex ligand sorbent system of CuAlCl '(toluene) grams (1 mole) of pure AlCl in 2 moles of benzene. The clear solution was then treated with pure ethylene to complex 2 moles of ethylene per mole of CuAlCl This solid complex was separated from the benzene, washed with pentane, which was saturated with ethylene, and was dried in a stream of pure ethylene. The ethylene was removed from the complex by heating under vacuum, leaving pure CuAlCl The solid was suspended in pure, dry, normal heptane such that a 50% by Weight slurry 1 100 mole percent.

EXAMPLE 5 In some cases, the recovery of higher molecular weight olefins (C is accompanied by alkylation of the aromatic diluent and by polymerization of the olefin if excess catalytic acidity is present in the sorbent preparawas obtained. Benzene, 0.1 mole, was added as an activator.

The slurry was stirred in a well agitated reactor, and a feed stream containing 50% ethylene and 50 ethane was passed through the slurry. The ethylene was absorbed until a complex was obtained which corresponded to 2 13 moles of ethylene per mole of bimetallic salt. (Complexation was carried out at ambient temperature and atmospheric pressure.)

The slurry was then heated to the boiling point of the heptane diluent and the complexed ethylene was evolved in better than 99% purity. The heptane diluent was stripped from the gas by an efiicient condenser. The decomplexed slurry was then capable of being returned to the complexer for another cycle.

EXAMPLE 8 Nuclear magnetic resonance studies A study was carried out of the exchange of a toluene complex of CuAlCL; to a propylene complex. 2 propyl- EXAMPLE l1 Complexing with CuAlBr A toluene complex of CuAlBr was prepared by slurrying together solid CuBr and solid AlBr in toluene at room temperature. The liquid (tolueneh-CuAlCl; complex formed readily and was used to recover and purify both CO and ethylene from their mixtures with non-complexing gases. Absorption was carried out at room temperature and atmospheric pressure while regeneration of the solution was carried out at 100 C. using nitrogen stripping gas.

eggs-gl-CuAlCl- (toluene) CuAlCh- (propylene) +2 tol- TABLE V u e Samples were prepared in a dry box which represented ff gas 50/50 C041? the initial toluene cuA1c1. complex and 25, 50, 7s and giailft.ii%;i?f.i%anaan;:31:31:11:13 100% exchange with propylene. These samples were 9 "9 e sealed in NMR tubes, and subjected to Proton NMR. The iigiaffff. 99.9+ 99.9+ ER E i 52 321i? i iiif lifliiasa t the Ethylmhmpy 1 1 amoun as exchange takes placg The propylene spectra are shifted These data Show that the bromine analog of CuA1C14 from that of pure propylene and indicate the donation of Works about the m as the 9111mm Compound and p electrons. be readily prepared m aromatic solvents. Furthermore, it

(2 The initial toluene spectra are shifted from that exchangs 'f W.1th other hgands' of free toluene and given only a single sharp peak. As the What IS damned 1s: exchange takes place, this peak changes and shifts to A process a Complemble hgand 10m that of free toluene so that no complexed toluene appears a f f contammg a hgand Selected from the group consisting of carbon monoxide, C -C acetylenes, C C present at the end of the exchange. 1 fi C C 1 1 fi C C I 1 (3) The exchange data confirm that two moles of 22 3 e 6 y i ggg zg 8 g gfz g gg 5- 10 a s hgand are exchanged dunng tha expenment which comprises contacting the feedstrearn with a sorbent EXAMPLE 9 comprised of a bimetallic salt having the generic formula Anene Moichiometry CuAlX wherein X is selected from the group consisting of chlorine, bromine and fluorine atoms, the contacting A solution of CuAlCl -(toluene) in excess toluene being effected under substantially anhydrous conditions, which contained 3.09 moles per liter of copper was used and forming a complex of the ligand and the sorbent. to absorb allene from a 50:50 allene-propane mixture at 2. The process of claim 1 wherein X is selected from room temperature and atmospheric pressure. The amount 40 the group consisting of chlorine and bromine atoms. of allene absorbed was calculated from analysis of the gas 3. The process of claim 1 wherein said complexible leaving the absorber and measurement of its volume. A ligand is selected from the group consisting of C -C total of 2.62 moles per liter of allene was absorbed correacetylenes, C C monoolefins and C -C conjugated sponding to a ratio of 2.62:3.09 or 0.85 mole of allene per diolefins. mole of Cu. This indicates an allene/Cu mole ratio of 4. The process of claim 2 wherein said complexible 1.0. ligand is selected from the group consisting of C -C EXAMPLE 10 acetylenes, C -C monoolefins and C -C conjugated di- Li and ex hange olefins' 5. The process of claim 4 wherein X is a chlorine atom.

Rapid ligand exchange has been demonstrated for a 6. The process of claim 5 wherein said complexible variety of pairs of complexing ligands. In these experiligand isaC C monoolefin. ments the (toluene) -CuAlCl complex was treated at 7. The process of claim 2 wherein said complexible room temperature in a gas bubbler with a gas containing ligand is a C C monoolefin. another ligand (either ethylene, CO, or acetylene) until 8. The process of claim 2 wherein said complexible the Cu would no longer pick up any of the gaseous ligand. ligand is ethylene.

Then a second gas containing a different complexing 9. The process of claim 2 wherein said complexible ligand was used to strip the solution and the exit gas was ligand is propylene.

analyzed by gas chromatography. Finally, when no further 10. The process of claim 1 wherein the sorbent is a changes in composition occurred, the solution was heated solid.

to 140 C. to liberate whatever was complexed on the 11. The process of claim 10 wherein the feedstream is CuAlCl This gas was also analyzed by gas chromatoga liquid and the contacting is effected at temperatures no raphy. The results are shown in the following table. more than about 30 F. above the dew point of the liquid.

TABLE N First eornplexing ligand Ethylene CO Acetylene.

Stripping gas Propylene. Ethylene. Ethylene.

First exit stripping gas 86.7% C2' 00.1% CO 82% 02.

Last exit stripping gas" 99.94% 03- 100% Cz' 99.06% C2 Decornplexed product 99.97% Ca 99.9+% Cr..." 98%(32', 2% C7E- This table shows that the first stripping gas analyzed 12. The process of claim 10 wherein the feedstream is from 82 to 90% content of the ligand which was used to gaseous,

form the original complex even though a different pure ligand was used as the stripping gas. This means that the few seconds needed for the gas to pass through the liquid are enough to get extensive ligand exchange. Furthermore,

13. The process of claim 1 wherein the sorbent is in the liquid phase.

14. The process of claim 13 wherein the feedstream is the very small amount of the original ligand obtained upon 7 5 gaseous.

15. The process of claim 13 wherein the feedstream is liquid.

16. The process of claim 1 wherein the sorbent is employed as a slurry and the slurry liquid is selected from the group consisting of C C paraflins, C C naphthenes, and mixtures thereof.

17. The process of claim 16 wherein the slurry contains an aromatic.

18. The process of claim 17 wherein the aromatic is a C -C aromatic and is present in an amount of at least about mole percent based on bimetallic salt in the sorbent.

19. A process for separating a complexibe ligand selected from the group consisting of C -C acetylenes, C C monoolefins, C -C conjugated diolefins, and carbon monoxide from a feedstream containing the ligand which comprises contacting, under substantially anhydrous conditions and at temperatures ranging from about --40 F. to about +300 F., the feedstrearn with a sorbent comprised of cuprous aluminum halide, and forming a complex of the sorbent and the ligand.

20. The process of claim 19 wherein said sorbent is selected from the group consisting of cuprous aluminum chlorides and cuprous aluminum bromides.

21. The process of claim 20 wherein said complexible ligand is a C -C monoolefin.

22. The process of claim 20 wherein said complexible ligand is selected from the group consisting of ethylene and propylene.

23. The process of claim 19 wherein the ligand is an olefin and the contacting is effected in the presence of a neutralizing agent selected from the group consisting of ammonia, C -C organic nitrogen bases, and Group V-B metal trihalides.

24. The process of claim 19 wherein the complex is separated from the feedstream and the ligand is recovered by decomplexing the complex.

25. A process for separating a complexible ligand selected from the group consisting of C -C acetylenes, C

C monolefins, C -C conjugated diolefins, and carbon monoxide from a feedstream containing the ligand which comprises contacting, under substantiallyv anhydrous conditions and at temperatures ranging from about F. to about +300 F., the feedstream with a CuAlCl (aromatic) sorbent, and exchanging the aromatic in the sorbent with the complexible ligand. T

26. The process of claim 25 wherein the aromatic, is toluene.

27. The process of claim 25 wherein said aromatic is selected from the group consisting of benzene and toluene and said complexible ligand is selected from the group consisting of ethylene and propylene.

28. The process of claim 25 wherein said aromatic is benzene.

29. The process of claim 25 wherein said complexible ligand isaC C monoolefin. p

30. The process of claim 1 wherein said sorbent is employed in the presence of an aromatic solvent. i

31. The process of claim 30 wherein said aromatic solvent is selected from the group consisting of Cs-Cgo aromatics.

References Cited UNITED STATES PATENTS 3,440,296 4/1969 Walker 260-674 3,467,725 9/ 1969 Walker 260--674 2,810,002 10/ 1957 Scott et al 260 674 3,517,081 6/1970 Beckham et a1. 260 -674 X DELBERT E. GANTZ, Primary Examiner G. E. SCHMITKONS, Assistant Examiner US. Cl. X.R. 

